The Most Unwanted
Zebra Mussels
The zebra mussel is a stripey, freshwater mussel native to Eastern Europe.
They spread naturally in water currents within connected lakes and river systems.
Outside connected waterways they are spread mainly by recreational activities such as boating and fishing. 
They form large colonies that attach to almost any hard surface such as rocks, boat hulls and jetties.
Northern Ireland is one of the most recent regions to have been invaded by Zebra Mussels.
They originate from the Caspian and Black Sea and spread across canal networks in Europe in the late 18th century, reaching England by 1824
They didn’t arrive in Ireland until 1994, and spread rapidly throughout the Shannon-Erne waterway and connected navigable water bodies.
In 2005 they were found in Lough Neagh.
Further details on Zebra Mussels can be found in the following documents:
- Zebra Mussel Management Strategy for Northern Ireland 2004-2010 (.PDF 532Kb)
- Management of the impacts of Zebra Mussels in Northern Ireland and determination of fish populations in Lough Erne through alterations of the food web (.PDF 516KB)
- Zebra Mussels Advice for Anglers and Water users (.PDF 571Kb)
- Zebra Mussel downloadable A3 poster (.PDF 490Kb)
Japanese Knotweed
Japanese knotweed (.PDF 392.83Kb), an invasive perennial plant, was first introduced into the UK in the 1820s as an ornamental garden plant.
It was subsequently spread intentionally to support steep banks and to provide screening before the negative impacts associated with it came to be known.
In it's home country of Japan it was an early coloniser of volcanic slopes where it is controlled by natural predators.
It’s natural enemies are not present in Northern Ireland so Japanese Knotweed plants thrive in our environment.
It is a tall ornamental plant growing to heights of 2.5 meters, forming dense thickets.
Only female Japanese knotweed plants are known to occur in the UK.
It is spread entirely by the movement of plant material or by the movement of contaminated soil material containing fragments of its extensive rhizome (underground roots) system.
It has many direct and indirect impacts on the environment and the economy, ranging from out-competing our native species to causing structural damage to buildings and bridges. It is very difficult to control but there are a few methods available.
Through the ‘Invasive species in Ireland Project' both a best practice guide on controlling Japanese Knotweed and. an information leaflet aimed at assisting gardeners has been produced.
Giant Hogweed
Giant Hogweed was first introduced as an ornamental garden plant from south west Asia in the 19th century. It is usually found along river banks, wasteland and road sides. It bears a close resemblance to Common Hogweed and Cow Parsley, but it is distinctive due to its huge size, often 3 to 5 metres tall and the leaves can grow up to 1.5 metres in width.
It flowers between June and September, producing several thousand seeds per plant. These seeds are then subsequently dropped near the adult plant leading to its gradual spread and invasion of an area.
It is best known to the public for the sap which it produces.
When the sap comes into contact with human skin, in the presence of direct sunlight, it can lead to severe blistering of the skin.
Serious infestations can lead to the closure of public footpaths and recreational areas.
Information on best practice control for Giant Hogweed
